Catalytic converter with housing-bed-plenum reinforcing and spacing means

ABSTRACT

In a catalytic converter, a sheet metal housing encloses a pair of sheet metal catalyst pellet beds and a stud extends through aligned openings in the members of the housing and both inner and outer member of each bed to reinforce these members and also maintain a certain spacing between the members of each bed. The inner bed members are self-piloted and fixed together in alignment at their respective stud openings prior to their assembly in the converter. An enlarged diameter portion is provided on the stud to maintain predetermined spacing between the inner and outer members of one of the beds and a spacer is added which cooperates with the enlarged diameter stud portion to hold the inner bed members in position while also maintaining a predetermined spacing between the members of the other bed. Then on external clamping of the housing members to the outer bed members at the stud, such clamping and spacing is permanently retained by welding the housing members to the ends of the stud.

This invention relates to catalytic converters for internal combustionengine exhaust gases and more particularly to such converters of thetype having a sheet metal housing enclosing a pair of sheet metalcatalyst pellet beds.

In catalytic converters of the above type, it is known that a stud maybe employed to provide reinforced support and spacing of the catalystbeds within the housing in addition to providing reinforcement of thelatter. However, in such arrangements where the beds have inner memberswhich separate the pellets in the beds and also cooperatively form aplenum therebetween for air injection into the exhaust gases passingfrom one bed to the other, it has been found that the conventional typeof stud if it is to provide support for these inner bed members is notthen effective to also maintain spacing in both the beds. Furthermore,there is a problem in assuring and maintaining alignment of the studopenings in the inner bed members in a practical way during assembly ofboth beds in the converter housing.

The present invention solves both such problems with a simplemodification of one of the inner bed members and the addition of aspacer sleeve. In the preferred embodiment of the present invention, aneck is formed integral with one of the inner bed members which extendsabout its stud opening and is formed over the edge of the stud openingin the other inner bed member whereby the inner bed members areself-piloted and fixed together at their stud openings prior to theirassembly in the converter. The stud is formed in a conventional way witha large diameter portion which abuts the oppositely facing inner sidesof the members of one of the beds to thereby maintain the predeterminedspacing therebetween. One end of the stud extends outward through thestud opening in the outer member of this one bed and also through thestud opening in one of the housing members. On the other hand, the otherend of the stud extends outward through the stud opening in both theinner bed members which have been previously aligned and securedtogether at this location. A spacer sleeve is received about the studand abuts at one end thereof with the inner side of the outer member ofthe other bed and at the opposite end thereof cooperates with the largediameter stud portion to sandwich both the inner bed memberstherebetween to thereby maintain the predetermined spacing between themembers of this other bed. Then on external clamping of the housingmembers to the outer bed members at the stud, this clamping and spacingis permanently retained by welding the housing members to the ends ofthe stud.

These and other objects, features and advantages of the presentinvention will become more apparent from the following description anddrawings in which:

FIG. 1 is a perspective view with parts broken away of a catalyticconverter embodying one form of the present invention.

FIG. 2 is a longitudinal sectional view taken along the line 2--2 inFIG. 1.

FIG. 3 is a cross-sectional view taken along the line 3--3 in FIG. 2.

FIG. 4 is an enlarged end view taken along the line 4--4 in FIG. 1.

FIG. 5 is an enlarged partial view taken along the line 5--5 in FIG. 3.

FIG. 6 is an exploded view of the converter in FIG. 1.

FIG. 7 is a perspective view with parts broken away of a catalyticconverter embodying another form of the present invention.

FIG. 8 is a longitudinal sectional view taken along the line 8--8 inFIG. 7.

FIG. 9 is a cross-sectional view taken along the line 9--9 in FIG. 8.

FIG. 10 is an enlarged partial view taken along the line 10--10 in FIG.8.

FIG. 11 is an exploded view of the inner bed members and air tube of theconverter in FIG. 7.

Each of the two catalytic converters shown is for use in a vehicle topurify the exhaust gases from an internal combustion engine. Bothconverters are of the dual-bed down-flow type with one bed retainingpellets P_(3W) coated with a 3-way catalyst and the other bed locateddownstream thereof and retaining pellets P_(O) coated with an oxidizingcatalyst and with the exhaust gases being directed downward through bothbeds. The converter shown in FIGS. 1-6 has a total bed capacity of about138 cubic inches for use with small engines of about 3.0 liters and lesswhile the converter shown in FIGS. 7-11 has a total bed capacity ofabout 250 cubic inches for use with larger engines. It will beunderstood, of course, that these sizes can vary dependent upon suchfactors as the catalyst, the particular engine and the emission levelssought.

The converter shown in FIGS. 1-6 has a generally rectangular box profileand comprises a sheet metal housing 10 of the clamshell type consistingof an upper shell member 11 and a lower shell member 12 made ofstainless steel. The housing shell members 11 and 12 have a body portion14 and 15, respectively, which cooperatively enclose a pair of sheetmetal catalyst beds or retainers 16 and 17 also made of stainless steel.In addition, the housing shell members 11 and 12 have semi-cylindricalneck portions 18, 19 and 20, 21 respectively, with the two neck portions18 and 20 cooperating on their concave side to form an inlet opening inone end of the housing and the other two neck portions 19 and 21cooperating on their concave side to form an outlet opening in theopposite end of the housing. Then for joining together the two housingshell members and mounting the catalyst beds therebetween, the housingshell members 11 and 12 are formed with integral co-planar flanges 27,28 and 29, 30, respectively, which extend horizontally between thehousing ends along opposite sides of the respective body portion 14, 15and neck portions 18, 19 and 20, 21.

The catalyst beds 16 and 17 consist of an upper and lower perforatedshell member 32 and 33 and an upper and lower perforated plate member 35and 36 with the bed plate members 35 and 36 located between or inward ofthe bed shell members 32 and 33 and the upper bed shell member 32 has abody portion 37 for retaining the 3-way catalyst pellets P_(3W) andaddition has an imperforate portion 38 at one end with asemi-cylindrical neck portion 39. The neck portion 39 nests on itsconvex side with the concave side of a semi-cylindrical neck portion 40formed on one end of the lower bed shell member 33. The latter neckportion 40 in turn nests on its convex side with the concave side of theneck portion 20 on the lower housing shell member 12. The lower bedshell member 33 in similar manner has a body portion 41 for retainingthe oxidizing catalyst pellets P_(O) and an imperforate portion 42 witha semi-cylindrical neck portion 43 on the lower bed shell member endopposite its neck portion 40. The neck portion 43 nests on its convexside with the concave side of a semi-cylindrical neck portion 44 formedon the end of the upper bed shell member 32 opposite its neck portion39. The neck portion 44 in turn nests on its convex side with theconcave side of the neck portion 19 on the upper housing shell member11.

In addition, the upper and lower bed shell members 32 and 33 haveco-planar flanges 46, 48 and 49, 50, respectively, which extendhorizontally along opposite sides of its respective body portion 37, 41and neck portions 39, 44 and 40, 43. The respective upper and lower bedshell member flanges 46, 48 and 49, 50 mate along their repective lowerand upper side except for the accommodation of an air tube between theflanges 48 and 50 as described later and also mate along theirrespective upper and lower side with the respective upper and lowerhousing shell flanges 27, 28 and 29, 30. These flanges are thus mated ina four-layer arrangement along the opposite sides of the housing andhave edges sealingly joined together external of the housing by separatewelds 54 and 56.

On the other hand, the outer bed members 32 and 33 form a three-layerarrangement with one of the housing shell members at each of the housingopenings to thereby provide complete peripheral support of the bedswithin the housing and also direct the exhaust gases entering thehousing first down through the 3-way catalyst bed 16 and then downthrough the oxidizing catalyst bed 17 and out of the housing. At theinlet end of the converter, the neck portion 39 on the upper bed shellmember 32, which is the top of the three-layer bed shell-housing shellmember arrangement at this end, cooperates on its concave side with thatof the neck portion 18 on the upper housing shell member 11 to provide acylindrical converter inlet 57 adapted to receive and be edge welded toa pipe (not shown) for connecting the converter into the exhaust systemto receive the exhaust gases from the engine. In addition, the outer bedside of the upper bed shell member 32 including its body portion 37 andimperforate portion 38 cooperates with the inner side of the upperhousing shell member 11 to form an upper space 58 within the housingdirectly open to only the housing inlet 57. The imperforate portion 38is slanted to funnel the exhaust gases upward into the space 58 and thebody portion 37 has a perforated top 60 which is flat except in the areaof stud openings as described later and except for the formation of aplurality of gas flow holes spaced over the area thereof formed byupwardly projecting louvers 62 which permit gas flow therethrough whileretaining the pellets in the upper catalyst bed 16. Thus, the exhaustgases entering the upper space 58 in the converter through the inlet 57are caused to flow down through the top of the upper catalyst bed 16.

In an inverse manner at the outlet end of the converter, the neckportion 43 on the lower bed shell member 33, which is the bottom of thethree-layer bed shell-housing shell member arrangement at this end,cooperates on its concave side with that of the neck portion 21 on thelower housing shell member 12 to provide a cylindrical converter outlet59 which is adapted to receive and be edge welded to a pipe (not shown)for conveying the purified exhaust gases from the converter into thedownstream portion of the exhaust system. The outer bed side of thelower bed shell member 33 including its body portion 41 and imperforateportion 42 cooperates with the inner side of the lower housing shellmember 12 to form a lower space 64 within the housing directly open toonly the outlet 59. The body portion 41 has a perforated bottom 66 whichis flat except in the area of stud openings as described later andexcept for the formation of a plurality of gas flow holes spaced overthe area thereof formed by downwardly projecting louvers 68 which permitgas flow therethrough while retaining the pellets in the lower catalystbed 17. Thus, the exhaust gases are caused to flow down through thebottom of the lower catalyst bed 17 to the lower space 64 and theimperforated portion 42 is slanted to direct the gases upward therefromto the outlet 59.

Furthermore, it will be seen in FIG. 3 that the outer bed member bodyportions 37, 41 have vertical imperforate sides which are spaced inwardfrom vertical sides of the respective housing member body portions 14,15 and that the corresponding vertical sides of the respective bedmember body portions and housing member body portions are verticallyaligned. In addition, it will be seen in FIGS. 2 and 4 that the oppositesides of the outer bed member body portions 37 and 41 are evenly taperedin height in opposite directions so that the perforated top 60 of theupper catalyst bed 16 is slanted to gradually decrease the overhead flowarea in the upper space 58 in the direction of the entering gas flowinto the upper bed while the perforated bottom 66 of the lower catalystbed 17 is slanted in the same direction and parallel to the top 60 ofthe upper bed to gradually increase the underneath flow area in thelower space 64 in the direction of the exiting gas flow from the lowerbed. With such arrangement, the total depth of the pellets in the twobeds 16 and 17 is made uniform thereacross and that coupled with theoppositely tapered flow areas above and below effects even distributionof the gas flow across the flow area of both beds.

The pellets P_(3W) and P_(O) in the two beds are separated and a plenumis provided therebetween for air injection by the two perforated innerbed members 35 and 36 cooperating with each other and with the outer bedmembers 11 and 12. Furthermore, the inner bed members 35 and 36 areperipherally mounted so that they are supported by the outer bed members11 and 12 and the housing shell members 11 and 12 while relativeexpansion with heat is permitted therebetween to maintain their sealedintegrities. The upper bed plate member 35 is flat except for areinforcement rib and accommodating a round air tube 69 as describedlater and except for the formation of gas flow holes spaced over thearea thereof formed by upwardly projecting louvers 70 which are locatedinward of a peripheral margin or flange 71 and permit gas flowtherethrough while retaining the pellets in the upper catalyst bed 16.The flange 71 on the upper bed plate member mates along its lower sidewith the upper side of a peripheral flange 72 formed on the lower bedplate member 36 and these flanges are spot-welded together at spacedpoints along their length after piloted assembly and flanged connectionof the inner bed members as described in detail later. The lower bedplate member 36 inward of its peripheral flange 72 has a perforatedportion 73 which is displaced or recessed downward and thus away fromthe lower side of the perforated portion of the upper bed plate member35 to provide a space or plenum 74 therebetween and thus between the twocatalyst beds 16 and 17 for air injection into the downwardly passingexhaust gases. The perforated portion 73 is flat except for a stiffeningrib and central projections and accommodating the air tube 69 asdescribed later and except for the formation of a plurality of gas flowholes spaced over the area thereof formed by downwardly projectinglouvers 75 which permit gas flow therethrough while retaining thepellets in the lower catalyst bed 17. Furthermore, it will be seen atthis point that the louvers in all the bed members extend transverselythereof with the louvers in the upper bed shell member thus extendingtransverse to the entering exhaust gases while the louvers in the lowerbed shell member extend transverse to the exiting exhaust gases.

The inner bed members 35 and 36 are supported, but not fixed, completelyalong the longitudinal portions of their mating flanges 71 and 72between the respective outer bed member flanges 46, 49 and 48, 50 andinward of the respective housing shell member flanges 27, 29 and 28, 30.For this purpose, there is formed a longitudinally extending recess 76,77 and 79, 80 in the lower and upper side of the respective inner bedmember flanges 46, 49 and 48, 50. The associated recesses 76, 79 and 77,80 form a pocket between the respective flanges 46, 49 and 48, 50 whichis located inward of where these flanges are welded to the housing shellmember flanges and which is open to receive the mating inner bed memberflanges. The vertical width of the pockets is sized so as to tightly butslidably receive the mating inner bed member flanges while a sufficienthorizontal end clearance 81 is provided therebetween so as to permitrelative sliding movement in the horizontal direction between theperiphery of the inner bed members and the outer bed members and thusalso between the periphery of the inner bed members and the housingshell members occasioned by relative heat expansion of these parts. Tothen complete the separation of the catalyst pellets in the beds, thereis formed a shoulder 82, 83 on and across the imperforate portion 38, 42of the respective outer bed members 32, 33 located immediately adjacentthe shallow end of the respective body portion 37, 41 of these members.The shoulders 82, 83 extend horizontally across the respectiveimperforate portions 38, 42 and join at opposite ends with therespective flanges 46, 48 and 49, 50 of the outer bed members. Theshoulders 82, 83 are co-planar with the bottom of the recesses 76, 77and 79, 80, respectively, in the flanges 46, 48 and 49, 50 with whichthey join and are located so that the shoulder 82 engages the upper sideof the flange 71 on the upper bed plate member 35 completely along itsend closest the inlet 57 while the other shoulder 83 engages the lowerside of the flange 72 on the lower bed plate member 36 completely alongits end closest the outlet 59. In addition, at the one end of therespective inner bed members 35 and 36 which is opposite but does notbear against the respective shoulders 82 and 83, there is formed adownwardly bent rib 86 and an upwardly bent rib 87, respectively, toreinforce the flange engagement of the inner bed plate members with therespective shoulders. Thus the separation of the pellets P_(3W) andP_(O) in the beds 16 and 17 is completed by cooperation of therespective outer bed member shoulders 82 and 83 with the mating innerbed member flanges 71 and 72 at the opposite ends of the inner bedmembers while the ends of the inner bed members and the respectiveimperforate portions 38 and 42 of the outer bed members are left free toexpand with heat relative to each other in the horizontal direction.Furthermore, it will be seen that with such shoulder engagement theupper bed shell member 32 at its imperforate portion 38 cooperates withthe body portion 41 of the lower bed shell member 33 in the formation ofthe lower catalyst bed 17 and also provides a place at this end of thelower catalyst bed out of the flow path therethrough through which thebed can be filled with pellets through the bottom of the converter asdescribed in detail later. In similar manner, the lower bed shell member33 at its imperforate portion 42 cooperates with the body portion 37 ofthe upper bed shell member 32 in the formation of the upper catalyst bed16 and also provides a place at this end of the upper catalyst bed outof the flow path therethrough through which the bed can be filled withpellets through the top of the converter as described in detail later.

Provision for the air tube 69 in the plenum 74 is provided by asingle-loop, partial-cylindrical imperforate channel 88 formed in theupper side of the recessed and otherwise perforated portion 73 of thelower bed plate member 36. The imperforate channel 88 extendslongitudinally of the recessed portion 73 from the end thereof closestthe converter inlet 57 to the opposite end thereof closest the converteroutlet 59 and then makes a reverse turn across the latter end andreturns longitudinally of the recessed portion and joins with a partialcylindrical channel 89 in and across the upper side of flange 72 at apoint located to one side of the converter inlet. The channel 88cooperates with the lower side of the perforated area of the upper bedplate member 35 to provide a U-shaped tube receiving cavity between theinner bed members 35 and 36 that is open on opposite sides to the plenum74 and is open at one end to a cylindrical opening between the inner bedmember flanges 71 and 72 provided by the channel 89 in flange 72cooperating with a partial-cylindrical channel 92 in and across thelower side of flange 71. Then for entry of the air tube through theconverter to the tube receiving cavity between the inner bed members,there is provided a partial-cylindrical channel 96 in and across theupper side of the lower bed shell member flange 50 and apartial-cylindrical channel 97 in and across the lower side of the upperbed shell member flange 48. The channels 96 and 97 cooperatively providea cylindrical opening therebetween directed at an angle toward theopening between the inner bed members provided by channels 89 and 92.And it will be seen that the lower channel 96 is made deeper than theupper channel 97 to accommodate for the downward displacement of thecenterline of the tube receiving cavity between the inner bed members 35and 36 relative to their mating flanges 71 and 72 so that the tubeopenings between the flanges of the inner bed members and the outer bedmembers 32 and 33 are vertically aligned. To then accommodate therespective channels 96, 97 between the housing shell members, thesechannels nest on their respective convex side with a partial-cylindricalchannel 98, 99 extending in and across the respective upper side of thelower housing shell member flange 30 and the lower side of the upperhousing shell member flange 28.

The round air tube 69 is made of stainless steel and is bent in aU-shape for mounting between the inner bed plate members 35 and 36 inthe tube receiving cavity provided in part by the imperforate channel88. The air tube 69 extends above the height of the channel 88 andengages along its length at diametrically opposite sides with the bottomof the channel and the flat lower side of the perforated area of theupper bed plate member 35 with such arrangement leaving oppositelyfacing side areas of the air tube above the channel exposed to theplenum 74. A plurality of holes 104 are formed in the thus exposed sideareas of the air tube at points spaced along the length thereof and arethus open to the plenum. The end 106 of the air tube within the plenumis closed by flattening thereof while the other end 107 is open and isprovided with an enlarged diameter adapted to receive a pipe (not shown)for delivering air thereto. The air tube where it extends outward of theplenum has an imperforate portion 108 which is tightly but slidablyreceived between the channel 92, 89 of the respective inner bed members35, 36 and then is bent to align with and be received between thechannels 97 and 96 of the respective outer bed members 32 and 33 withits open end 107 terminating at the edges of the outer bed shell memberflanges 48, 50 and housing shell member flanges 28 and 30. With the airtube thus installed a weld 109 is then made external of the housingbetween the pipe 108 and the edge of the open end of the air tube 69 andthose of the nesting channels 96, 98 and 97, 99 of the outer bed membersand the housing shell members. Thus, the air tube is sealingly fixed tothe converter housing and the outer bed members but is free to expandwith heat internally thereof both with and relative to the inner bedmembers while also maintaining the spacing therebetween in the plenum.Furthermore, it will be seen that with such mounting of the air tube 69between the inner bed members 35 and 36 and the location of the holes104 therein, the air is injected transversely into the exhaust gasesover the entire volume of the plenum and immediately after leaving theupper catalyst bed 16 for uniform and early mixing with the exhaustgases passing to the lower catalyst bed 17 while the perforated area ofthe upper bed plate member 35 is permitted to extend over the top sideof the air tube to minimize restriction to flow through the uppercatalyst bed.

Reinforced support and spacing of the catalyst beds 16 and 17 within thehousing 10 coupled with reinforcement of the latter is provided by apair of identical studs 110 which extend vertically through alignedopenings in the sheet metal members of the housing and both of thecatalyst beds. The studs are located centrally cross-wise of theconverter between the legs of the air tube 69. At each of the studlocations (see FIGS. 5 and 6), the lower bed plate member 36 is formedwith an upwardly projecting cylindrical neck 115 having a reduceddiameter portion 116 about its stud opening 117 which is closelyreceived by the stud opening 118 in the upper bed plate member 35. Aftermounting the air tube 69 between the inner bed members 35 and 36, thereduced diameter neck portion 116 is positioned to extend upward andthrough the stud opening 118 in the upper bed plate member 35 whereafterit is crimped over the edge thereof while the neck 115 engages the lowerflat side of the upper bed plate member to maintain the height of theplenum 74 at this location. The inner bed members 35 and 36 with the airtube 69 mounted therebetween are thus piloted into alignment and fixedtogether at their stud openings whereafter their flanges 71 and 72 arespot-welded prior to mounting of the inner bed members with the air tubeas a completed subassembly between the outer bed members 32 and 33.

The studs 110 have a short and long cylindrical portion 120, 122 ofequal diameter extending inward from the respective lower and upper endthereof separated by an intermediate cylindrical portion 124 of largerdiameter which serves as a spacer for the lower bed. Each of the studs110 is first located between the lower bed plate member 36 and the lowerbed shell member 33 whereafter its lower end with the short smalldiameter portion 120 may then be inserted downward or outward throughthe respective openings 126, 127 therefor in the lower bed shell member33 and lower housing shell member 12 while the stud's upper end with thelong small diameter portion 122 may then be inserted upward or outwardthrough the respective openings 117 and 118 in the previously securedtogether inner bed members 36 and 35. Next, a hollow cylinder or sleeve128 which serves as a spacer for the upper bed is mounted on the longsmall diameter stud portion 122 between the upper bed plate member 35and the upper bed shell member 32. Then the upper stud end with the longsmall diameter stud portion 122 may be inserted upwardly or outwardlythrough the respective opening 130 and 132 therefor in the upper bedshell member 32 and upper housing shell member 11.

Each of the stud openings 127, 132 in the respective lower and upperhousing shell members 12, 11 is located in the center of a separatesubstantially conical recessed area 134, 136 formed in the bottom andtop of the respective housing shell members. The respective housingshell member recessed areas 134, 136 have an outwardly projecting neck137, 138 about their stud opening 127, 132 for receiving the respectiveshort and long small diameter stud portion 120, 122 and bear on theirinner side directly against the lower side and upper side of therespective outer bed members 33, 32. In addition, the respective outerbed members 32 and 33 are formed with an upwardly and downwardlyprojecting neck 140 and 142 about their respective stud openings 130 and126. The necks 140 and 142 engage the respective lower and upper side ofthe housing shell members 11 and 12 and for that purpose their heightsare different to accommodate for the slant of the converter beds. Thus,at the left-hand stud as seen in FIGS. 5 and 6, the lower neck 142 isshorter than the upper neck 140 with this relative dimensioning reversedat the right-hand stud. A washer 146 is then located about each of thehousing shell member necks 137 and 138 and against the lower and upperside of the respective housing shell members 12, 11.

The axial lengths of the large diameter stud portion 124 and the sleeve128 are determined so that when the converter assembly is clampedtogether at the washers 146 the axially spaced annular shoulders 149 and150 of the large diameter stud portion 124 abuts with the oppositelyfacing inner sides of the lower bed members 33 and 36 to maintain thedesired spacing therebetween while the upper annular end 151 of sleeve128 abuts with the inner side of the upper bed shell member 32 and thelower annular end 152 of the sleeve cooperates with the upper studshoulder 150 to sandwich the two inner bed members 35 and 36therebetween at their flanged connection to maintain the desired spacingbetween the upper bed members 32 and 35. With the assembly thus clamped,a continuous weld 153 is provided between the respective projecting endsof the stud, the housing necks 137, 138 and the inner diameter of thewashers 146 to thus seal the converter at these stud locations whilefixing the stud 110 and sleeve 128 in place to maintain the clampedcondition and thus the bed spacing in addition to strengthening thehousing.

Filling of the upper catalyst bed 16 is provided through the top of theconverter by an opening 156, 157 in the respective upper housing shellmember 11 and upper bed shell member 32 adjacent the converter outletwith the upper housing member having a downwardly projecting neck 158about its opening which extends through and is crimped over the edge ofthe opening 157 in the upper bed shell member 32. After the upper bedhas been filled with the catalyst coated pellets P_(3W), the openingthereto is closed by a sheet metal plug 159 of stainless steel. On theother hand, the lower catalyst bed 17 is filled through the bottom ofthe converter by an opening 160, 161 in the respective lower housingshell member 12 and lower bed shell member 33. The opening 160 in thelower housing shell member 12 is provided with an upwardly projectingneck 162 thereabout which extends through and is crimped over the edgeof the opening 161 in the lower bed shell member 33. After the lower bedhas been filled with the catalyst coated pellets P_(O), the openingthereto is closed by a sheet metal plug 163 of stainless steel.

The converter housing is insulated by two sheets 164 and 165 of heatinsulating material which respectively lay across the top and bottomthereof and are held in place by a pair of sheet metal cover members 166and 167 of aluminum coated steel and of which only the upper covermember is ribbed in the transverse direction for strength. The covermembers 166 and 167 generally conform to the outer profile of theconverter housing while leaving the inlet, outlet and air tube open. Thecover shell members are spaced outwardly from the sides of the housingand are joined together by crimping flanges 168, 170 on the top covermember over flanges 172, 174 on the lower cover member at the weldedflanges of the housing shell members and outer bed members. In addition,the cover members 166 and 167 have a fill opening 176 and 178therethrough, respectively, and fit under the flange of the respectiveplugs 159 and 163 whereby the cover members are secured to the converterat these points when the plugs are inserted while leaving access throughthe cover for filling the catalyst beds.

Turning now to the larger size catalytic converter shown in FIGS. 7-11,the parts thereof similar to those of the converter in FIGS. 1-6 andpreviously described are identified by the same numbers but primed whiledifferent structural features as will now be described are identified bynew reference numbers.

In the catalytic converter shown in FIGS. 7-11 the housing 10' andcatalyst beds 16' and 17' are scaled up in size so as to provide asubstantially larger bed area and thus increased bed volume withoutsubstantial change in converter height. This is accompanied by acorresponding increase in flow area across the plenum 74' wherein thelouvers 70' in the upper bed plate member 35' are now located in anupwardly recessed area 200 inward of the flange 71' while maintainingthe same height in the plenum. This is accomplished by making the depthof the recessed perforated portion 73' one-half that in the converter inFIGS. 1-5 and making the depths of the recessed perforated portion 200in the upper bed plate member 35 the same as that of the recessedperforated portion 73'. And to then connect the inner bed members 35'and 36' as before at their respective stud openings 118' and 117', theheight of the necks 115' on the lower bed plate member 36' arecorresponding reduced while a downwardly projecting neck 201 of equalheight if now provided about each of the stud openings 118' in the upperbed plate member 35'.

Air distribution within the large plenum 74' is provided by a roundS-shaped air tube 202. To accommodate the S-shaped tube 202 in theplenum 74', both the inner bed members 35' and 36' are provided on theirinner or plenum side with a double-loop, partial-cylindrical imperforatechannel 203 and 204, respectively. The imperforate channels 203 and 204are formed in the respective lower and upper side of the recessed andotherwise perforated portion 200 and 73' of the respective inner bedmembers 35' and 36'. The imperforate channels 203 and 204 extendlongitudinally of the respective recessed perforated portions 200 and73' from the end thereof closest the converter inlet 57' to the oppositeend thereof closest the converter outlet 59' and then make a reverseturn and return centrally thereof. The channels 203 and 204 then make asecond reverse turn and return longitudinally of the respective recessedperforated portions 200 and 73' to join with the respectivesemi-cylindrical channels 92' and 89' which form the cylindrical openingbetween the inner bed plate member flanges 71' and 72'. The imperforatechannels 203 and 204 cooperate to provide an S-shaped tube receivingcavity between the inner bed members 35' and 36' that is open onopposite sides to the plenum 74'. The air tube 202 engages along itslength at diametrically opposite sides with the bottom of the respectivechannels 203 and 204 while leaving oppositely facing side areas thereofexposed to the plenum 74'. A plurality of diametrically opposite facingholes 206 are formed in the thus exposed areas of the air tube at pointsspaced along the length thereof and are thus open to the plenum. The end208 of the air tube within the plenum is closed by flattening thereofand is bent so that it hooks to the lower bed plate member 36' through ahole 210 provided in the recessed perforated portion 73' thereof wherebythe closed end of the tube is thus restrained. On the other hand, thetwo bends 212, 214 and 216, 218 of the respective imperforate channels203 and 204 have an enlarged cross-section to accommodate relativeexpansion with heat between the air tube 202 and the two inner bed platemembers 35' and 36'. The air tube 202 where it extends outward of theplenum has an imperforate portion 220 which is tightly but slidablyreceived between the channels 89' and 92'. The imperforate tube portion220 is bent for alignment with and mounting between the nesting outerbed members and housing shell member channels 97', 99' and 96', 98' withthe open and enlarged end 222 of the S-shaped tube 202 then fixed andsealed thereto and to the air delivery pipe 108' by weld 109 109' likethe U-shaped tube 69 previously described. However, it will be seen thatthe center-line of the tube receiving cavity between the inner bedmembers 35' and 36' now aligns with their mating flanges 71' and 72' andas a result the tube accommodating channels across the flanges of theouter bed members 32' and 33' and the housing shell members 11' and 12'are now semi-cylindrical to provide for vertical alignment of the tubeopenings which they form.

Reinforced support and spacing of the catalyst beds 16' and 17' withinthe housing 10' coupled with reinforcement of the latter is provided byfour studs 110' and associated structure like that earlier described.The studs 110' are located for best effect at points spacedlongitudinally of and between adjacent legs of the S-shaped air tube202.

The above described embodiments are illustrative of the invention whichmay be modified within the scope of the appended claims.

The embodiments of the invention in which an exclusive property orprivilege is claimed are defined as follows:
 1. In a catalytic converterfor internal combustion engine exhaust gases and of the type having asheet metal housing enclosing a pair of sheet metal catalyst pellet bedswith a stud extending through aligned openings in the members of thehousing and both the inner and outer members of each bed to reinforceall these members and also maintain a certain spacing between themembers of each bed and wherein the inner bed members also cooperate toform a plenum between the beds: the improvement comprising incombination, a neck integral with one of the inner bed members andextending about its opening and formed over the edge of the opening inthe other inner bed member whereby the inner bed members are fixedtogether in alignment prior to their assembly in the converter, firstspacer means integral with the stud for abutting oppositely facing innersides of the members of one of the beds to thereby maintain apredetermined spacing therebetween, one end of the stud extendingoutward through the opening in the outer member of said one bed and alsothrough the opening in one of the housing members, the other end of thestud extending outward through the opening in both of the inner bedmembers and also through both the opening in the outer member of theother bed and the opening in the other housing member, and second spacermeans received about the stud and abutting at one end thereof with theinner side of the outer member of said other bed and at the opposite endthereof cooperating with said first spacer means to sandwich both theinner bed members therebetween to thereby maintain a predeterminedspacing between the members of said other bed and whereby on externalclamping of the housing members to the outer bed members at the stud,such clamping and spacing is permanently retained by fixing the housingmembers to the ends of the stud.
 2. In a catalytic converter forinternal combustion engine exhaust gases and of the type having a sheetmetal housing enclosing a pair of sheet metal catalyst pellet beds witha stud extending through aligned openings in the members of the housingand both the inner and outer members of each bed to reinforce all thesemembers and also maintain a certain spacing between the members of eachbed and wherein the inner bed members also cooperate to form a plenumbetween the beds: the improvement comprising in combination, a neckintegral with one of the inner bed members and extending about itsopening and formed over the edge of the opening in the other inner bedmember whereby the inner bed members are fixed together in alignmentprior to their assembly in the converter, axially spaced annularshoulders on the stud abutting oppositely facing inner sides of themembers of one of the beds to thereby maintain a predetermined spacingtherebetween, one end of the stud extending outward through the openingin the outer member of said one bed and also through the opening in oneof the housing members, the other end of the stud extending outwardthrough the opening in both of the inner bed members and also throughboth the opening in the outer member of the other bed and the opening inthe other housing member, and a spacer sleeve received about the studand abutting at one annular end thereof with the inner side of the outermember of said other bed and abutting at the opposite annular endthereof with said neck of said one inner bed member to thereby maintaina predetermined spacing between the members of said other bed andwhereby on external clamping of the housing members to the outer bedmembers at the stud, such clamping and spacing is permanently retainedby fixing the housing members to the ends of the stud.